Ab Initio Reaction Kinetics of $CH_{3}O\dot{C}(=O)$ and $\dot{C}H_{2}OC(=O)H$ Radicals [electronic resource]

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Tác giả:

Ngôn ngữ: eng

Ký hiệu phân loại: 547.6 Aromatic compounds

Thông tin xuất bản: Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2015

Mô tả vật lý: Size: p. 1590-1600 : , digital, PDF file.

Bộ sưu tập: Metadata

ID: 263602

 In this work, The dissociation and isomerization kinetics of the methyl ester combustion intermediates methoxycarbonyl radical ($CH_{3}O\dot{C}(=O)$) and (formyloxy)methyl radical ($\dot{C}H_{2}OC(=O)H$) are investigated theoretically using high-level ab initio methods and Rice?Ramsperger?Kassel?Marcus (RRKM)/master equation (ME) theory. Geometries obtained at the hybrid density functional theory (DFT) and coupled cluster singles and doubles with perturbative triples correction (CCSD(T)) levels of theory are found to be similar. We employ high-level ab initio wave function methods to refine the potential energy surface: CCSD(T), multireference singles and doubles configuration interaction (MRSDCI) with the Davidson?Silver (DS) correction, and multireference averaged coupled-pair functional (MRACPF2) theory. MRSDCI+DS and MRACPF2 capture the multiconfigurational character of transition states (TSs) and predict lower barrier heights than CCSD(T). The temperature- and pressure-dependent rate coefficients are computed using RRKM/ME theory in the temperature range 300?2500 K and a pressure range of 0.01 atm to the high-pressure limit, which are then fitted to modified Arrhenius expressions. Dissociation of $CH_{3}O\dot{C}(=O)$ to $\dot{C}H_{3}$ and CO<
 sub>
 2<
 /sub>
  is predicted to be much faster than dissociating to $CH_{3}\dot{O}$ and CO, consistent with its greater exothermicity. Isomerization between $CH_{3}O\dot{C}(=O)$ and $\dot{C}H_{2}OC(=O)H$ is predicted to be the slowest among the studied reactions and rarely happens even at high temperature and high pressure, suggesting the decomposition pathways of the two radicals are not strongly coupled. The predicted rate coefficients and branching fractions at finite pressures differ significantly from the corresponding high-pressure-limit results, especially at relatively high temperatures. Finally, because it is one of the most important $CH_{3}\dot{O}$ removal mechanisms under atmospheric conditions, the reaction kinetics of $CH_{3}\dot{O}$ + CO was also studied along the PES of $CH_{3}O\dot{C}(=O)$
  the resulting kinetics predictions are in remarkable agreement with experiments.
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